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  1. PhilipFry

    Fundamental Question about Dynamic Pressure.

    Alright, I can't believe I need to ask this question, but I'm looking at the term in Bernoulli's equation for dynamic pressure (1/2*rho*velocity^2). Can someone explain to me the units on this this? When I look closely, it looks like it gives the answer as a unit of force, not pressure...
  2. PhilipFry

    Stress Strain Curve for Al 6061-T4?

    Howdy, Does anyone know where I can find a stress strain curve for Al 6061-T4. I've been able to find 6061-T6 relatively easily, but T4 is giving me fits! Thanks in advance! PJF
  3. PhilipFry

    What do you do when you don't trust your boss?

    My boss (stress analyst) has made several assumptions that have been flat out wrong. It appears to the rest of the team that these assumptions have been made in order to reduce our calculated stresses. Word of SOME (not all) of these assumptions have reached upper management and we've been...
  4. PhilipFry

    Can MSC Nastran solution 600 handle 1D gap elements?

    Because, I heard that it can't. Is that true?
  5. PhilipFry

    Stress Concentration in Aluminum T-Joints

    Hi. I'm still a bit new to the stress world, but I think I know just enough to get me into trouble. We've been discussing stresses in t-joints here recently and it came up that we should not be looking at the peak stresses in the fillets for static loads. It's been suggested that we use the...
  6. PhilipFry

    Aluminum Weld Shear Strength?

    Here's an easy question. I'm using 4043 to weld two 6061-T6 tubes and I'm trying to figure out the strength of the weld. I've found some literature that says the minimum shear strength of a weld using 4043 is 15 ksi. Does that figure include the weld efficiency, or would I need to knock that...
  7. PhilipFry

    Sweeping and changing cross-sections.

    I'm trying to accurate model the bend of a tube. The cross section of the tube initially starts out as a circle in the straight portions of the tube. It becomes more of an oval in the bend, and has peak ovality at the 45 degree mark in the bend. How should I go about doing this?
  8. PhilipFry

    Bolt Holes: Accuracy vs Computational Speed?

    I'm new to the stress world as of a few months ago. We are currently using Patran/Nastran to do our FEM on brackets and tubing. One of the big questions we are having at the moment is how accurate our current modeling techniques are. We usually make an RBE2 inside the bolt hole and then...
  9. PhilipFry

    Waterfall Plot

    Does anyone know how to get a waterfall plot out of mathcad? I have it set up to solve FFTs for only 1 speed at a time, but would like to be able to map it out.
  10. PhilipFry

    Free sample?

    Well I've completed my dynamic model, which, if correct, may play a big role in how critical speeds are found from now on. The problem now is actually getting a hold of some gears to test the theoary out. Where can I go to get some decent sized spur gears for inexpensive...or better yet...free...
  11. PhilipFry

    Another silly question I'm sure

    Okay, I've searched high and low here, but have come up scratching my head. I know you can determine that point of initial contact between spur gears based on the addendum circle and the line of action. But how do you determinem where the contact zones are? I know the contact ratio gives you...
  12. PhilipFry

    Trying to develope a dynamic model...

    I'm attempting to develope a dynamic model of a pair of spur gears by treating the bearings and gear teeth as springs. I had originally intended on building a simple system where only two gear teeth were in contact at any time, but now I'm hoping to expand my model to include three pairs of...
  13. PhilipFry

    Second Order Eigenvalues

    I'm new here to mathcad and I'm trying to find the eigenvalues of a second order spring/mass system without damping. I have a 6 by 6 matrix and I would prefer not to solve it symbolically because the solution would be too long. Is there a command to solve this system, or do I need to refresh...
  14. PhilipFry

    Area moment of inertia

    Hey, I'm trying to calculate the stiffness of a spur gear tooth, but am having a little trouble finding the second moment of inertia (I). Do I need to pull out my calculus book or is there already an equation for it laying around? I've looked in the machinery's handbook without much success.
  15. PhilipFry

    Pattern a loft?

    Is it possible to make a circular pattern of a loft? I'm trying to pattern a bracket I made with the loft function around a cylinder, but I get the following error: "Unable to create contour geometry. Please check the loft section." What part of the loft section am I suppose to check?
  16. PhilipFry

    Design a gear train

    Well, I think I'm starting to catch on with this gear stuff. I've been trying to design a gear train off the seat of my pants using a spreadsheet that I've been assembling to calculate bending and shear stresses. I've been comparing my answer to Fairfield's program, but this has been a...
  17. PhilipFry

    Outline Factor or Tooth Form Factor?

    Okay, I have a gear train that was designed by an engineer some time ago. Problem is, I can't find any documentation (if there ever was any) to help me determine the performance of the system. Therefore, I'm trying to use the Lewis Formula to come up with a rough idea of the required yield...
  18. PhilipFry

    Need a little help with choosing gear layout

    I've recently started working on a project here at work that would use a rack and pinion system. Can you offer some suggestions on how to design a system? In other words, how do you choose your gear size, profile, tooth thickness, number of teeth, etc.
  19. PhilipFry

    Creating a Pipe in an assembly

    I'm trying to create a pipe/tube to connect two arbitrary shapes in an assembly which aren't in the same plane. Is there an easy way of doing this with a 3d sketch/sweep (or any other method) without having to dimension the entire drawing? Is the piping add-in a possibility? If so, how do I...
  20. PhilipFry

    Importing dwg and text

    Is there a known solution to fix the "carriage return" problem when importing a dwg into microstations? Whenever I import a file, the dimension text, or annotation text, is spaced down a line for each space between words: STUB ACME becomes: STUB ACME Any ideas? --Mike

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